Bandwidth Enhancement of Extended Interaction Klystron by Ridge-Loaded Extended Interaction Cavity

A scheme of symmetric ridge loading of the top and bottom shorting cavities of an extended interaction cavity is proposed in this article for the broadbanding of an extended interaction klystron (EIK). While implementing this scheme, the periodicity of the ladder circuit has not been changed. In order to demonstrate the efficacy of the ridge loading in broadbanding, 3-D electromagnetic analysis was carried out on a W-band extended interaction cavity structure. The ridge loading is found to reduce the ohmic quality factor of the extended interaction cavity by 25% against that of no loading for the cavity operating at 95 GHz. At the same time, the ridge loading has shown marginal changes on the characteristic impedance and the peak axial electric field of the structure. A particle-in-cell (PIC) analysis has shown an enhancement in the 3-dB hot bandwidth of the ridge-loaded EIK (464 MHz) by around 250% in comparison to an unloaded device (185 MHz).